In the art of metal extrusion, especially aluminum extrusion, it is well known that the billet to be extruded is heated to an elevated temperature, in the range of 800.degree. F. for example. Although preheating of the billet is considered highly desirable or even necessary for extrusion operations, it also is known to introduce certain problems due primarily due to the sticky or tacky nature of the heated billet. For example, one common problem has been the tendency of a billet butt to cling to the shear blade after it has been sheared from the extrusion die face after extrusion of the billet. This has resulted in the need for butt knockoff bars and other similar expedients to insure that the billet butt does not remain hung up on the shear blade.
Another problem resulting in large part from the tacky property of a heated billet is that the closing plate which closes the rear end of the extrusion container in indirect extrusion tends to adhere to the rear end of the billet. In the case of direct extrusion, the same problem appears in the interface between the rear end of the billet and the dummy block which resides between the billet and the extrusion stem.
As a solution to this problem, it is known to lubricate the interface between the billet and the dummy block or closing plate by applying lubricant to the billet. Typically, and especially for fixed dummy arrangements, only one of a given number of billets in a sequence of billets needs to be lubricated as the lubricant from a billet will transfer to the dummy block and will be effective for lubrication of a number of subsequent billets. The prior practice of billet end lubrication has included, for example, manual lubrication by the press operator during an interruption in the transfer cycle which transfers the billet from the billet shear into the extrusion press. This approach has been viewed as inefficient and therefore undesirable.
Another prior means of billet end lubrication has been the use of a gas burner which burns acetylene gas to produce carbon for deposit on the billet end by projecting the acetylene flame at the billet end. This approach also is inefficient and is undesirable due to the open flame of the burner. In addition, as with the above mentioned manual lubrication approach, interruption of the billet transfer cycle is undesirable. Furthermore, the acetylene flame produces much unnecessary airborne particulte contamination.
Still another problem of prior billet lubrication schemes has been the common use of hydraulic fluid drive for the billet transfer mechanism. Due to the large magnitude of hydraulic pressure forces utilized (e.g. 3600 psi) hydraulic fluid power is not preferred as a careless worker could sustain injury in working around the large, hydraulically driven transfer components. Nevertheless, in another sense hydraulic power is preferred to provide a uniform, repeatable mid-cycle stopping point for the billet transfer mechanism to accommodate the desired billet lubrication. This is especially true if billet lubrication is performed by a device located at a predetermined position with respect to the transfer cycle.
By contrast, air power cannot provide the desired repeatability due to the compressability of the air and the massive loads the air is moving. When attempting to stop the billet transfer cycle in midstroke under air power, the transfer carriage will tend to drift from the desired position and thus will not remain in alignment with a relatively stationary lubrication apparatus.